According to the CDC, the MMR vaccine is not 100 percent effective at protecting against mumps. Both doses of the MMR vaccine offer 88 percent effectiveness, while one dose offers 78 percent effectiveness.

Mumps is highly contagious, easily spread in close-contact settings.

Sports teams like in the NHL and university settings can be the perfect breeding ground for mumps.

“You can get it after the person's left the room, if you touch their contaminated dish or fork or soda can. There’s saliva on the surface and then you touch your mouth,” Dr. Lynch explained.

You may be contagious for up to 25 days before you even know you're sick.

Dr. Lynch said high vaccination rates should help limit the spread of the outbreak.

But we could see large outbreaks in areas with higher numbers of unvaccinated people.